The present invention relates to a one-piece combination of a plastic lid and a pour spout which are molded in a single molding operation from two different plastic materials. While the invention may have broader application, it will be described here in conjunction with a plastic lid and a flexible plastic pour spout which is integral with the lid and can be collapsed to a relatively flat position and can be pulled out to an extended position when it is desired to pour liquid from a bucket which is closed on the top by the lid.
Such a pour spout must have a relatively thin spout section to permit it to be pressed into a generally flat or collapsed position when not in use, and to be pulled out to an extended position when the spout is to be used for pouring from a bucket on which the lid is attached. In contrast, the plastic lid must be more rigid than the pour spout.
It has been known heretofore to mold a pour spout and attach it to a lid. Thus, the lid and pour spout are molded separately, and then an operation is carried out to attach the pour spout to the lid. Where a pour spout is to be used, the lid must be molded with a fitting to which the pour spout can be attached. Such a fitting will normally include a solid portion which can be punched out to create a hole where the pour spout attaches. The pour spouts have their own screw cap or the like for closure. If no pour spout is utilized, the lid can function as a normal closure for an open top bucket.
Known pour spouts comprise relatively soft, thin plastic in the spout area, combined with a relatively rigid base portion which attaches to the lid fitting. Such a base portion may be made of metal, or relatively rigid plastic. Known pour spouts also have a screw-on cap so the spout can be opened and closed. In some cases, the spout will snap onto a fitting portion on the lid, while in other cases the spout may screw on to the lid fitting. In all such cases, the pour spout is attached to the lid after the lid has been molded, and such pour spouts are relatively expensive.
The known pour spouts have significant disadvantages. As noted above, they are relatively expensive, and of course an attachment operation is required after the lid is molded. Beyond that, plastic bucket and lid combinations are often required to be subjected to drop tests to assure that filled buckets can withstand a given drop without the lid disengaging or any of the contents being lost. The various known spouts as described above which snap or screw on to a lid fitting have not performed well when subjected to required drop tests. In addition, there is a theft problem because the relatively expensive pour spouts can easily be removed from the lid fitting.
It is also known to mold a plastic lid, and to connect a molded pour spout to such a lid by fusing or welding the pour spout to a fitting formed on the lid. Such a method also involves attaching the pour spout to a lid after the lid is molded.
Another known technique involves connecting a previously molded pour spout to a lid during the molding of the lid. The foregoing known technique utilizes a pair of mold inserts which position a previously molded pour spout in a lid mold during molding of a lid, and the pour spout is positioned so that the lid plastic will surround an annular projecting rim or flange at the base of the pour spout to fuse the lid to the pour spout.
An improvement over the foregoing known technique is disclosed in the inventor's co-pending U.S. patent application, Ser. No. 09/106,231, filed Jun. 29, 1998. In the co-pending application, there is disclosed an improvement for mechanically interconnecting a pour spout to a lid during the molding of the lid. Such a technique offers the advantage that the connection between the pour spout and the lid is not created solely by fusion, but rather involves a mechanical interconnection.
The known techniques for providing a plastic lid with a plastic pour spout fall basically into two categories. In one case, a pour spout and a lid are molded in separate operations and the two molded articles are subsequently attached. In the second case, a pour spout is molded first, and then the previously molded pour spout is fused or interconnected to a lid during the molding of the lid.
None of the foregoing known techniques involves the basic concept of the present invention which is to mold a pour spout and a lid from two different plastic materials in a single molding operation which produces a one-piece lid with an integral pour spout.
In accordance with the present invention, a dual extruder plastic injection molding machine is used which can independently control the timing and shot size of the first and second plastic materials in a manner as to fuse or blend the two plastic injected materials at a predetermined location of the combined one-piece, molded article.
While a two-shot molding machine which will inject two different plastic materials is known, the usual technique involves injecting the first plastic material, and then after the first shot, core pulls are mechanically moved in preparation for the second shot. However, in accordance with the present invention, the two shots of two different plastic materials may be performed substantially simultaneously without the use of any mechanical moving core pulls in either one of the two mold valve gates.
In accordance with the present invention, a one-piece plastic lid and spout is produced having a spout portion of a flexible material and the lid made of a more rigid plastic. Such a product will pass the test requirements of the packaging industry.
It is preferred that injection of each plastic be independently programmed. For optimum results, an operator practicing the present invention can consider the speed, injection pressure and timing of each of the two injection systems and thereby evaluate the flow characteristics, the flow distance, and the location and conditions of the melt where the two plastic materials meet to insure a good mixed blend and optimum fusion of the two plastic materials.
The present invention involves providing one spout injection system which injects plastic directly into the center of the spout cavity while at the approximate same time a second independent lid injection system is operated to inject a different plastic material at the center of the lid cavity.
An important advantage of the present invention is that it produces a one-piece lid and integral pour spout made of two different plastic materials where the spout and lid are fused in an improved manner to eliminate leakage between them.
Another advantage is that the fusion between the lid and pour spout is improved over previously known techniques so that improved drop test results are achieved where the pour spout will not pop off the lid even under severe testing conditions.
One reason for the foregoing advantages is because the present invention involves the fusing of two hot plastic materials which can readily fuse with one another. The previously known fusion techniques involved fusing of a previously molded pour spout, so that even when such fusion is accomplished during molding of the lid, the fusion still must occur using a relatively cold pour spout which was molded in a prior molding operation.
Still another advantage of the present invention is reduction of molding cost due to the avoidance of requiring two separate molding operations to produce the pour spout and the lid. The present invention requires only a single molding operation.
The foregoing and other objects and advantages of the invention will be apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings.